Porenwasser

Porenwasser (pore water) is the water that occupies the voids within porous materials such as soils and rocks. It is one component of a material’s moisture state, with the other being pore air. In saturated conditions, all voids are filled with water; in unsaturated conditions, water and air share the pore volume. The pressure of pore water, called pore-water pressure, influences the stress state of the solid framework through the concept of effective stress: σ' = σ − u, where σ is total stress and u is pore-water pressure.

Pore-water pressure is central to drainage, consolidation, seepage, slope stability, and liquefaction phenomena. The hydraulic head, h, combines elevation z and the pressure head ψ, representing the energy state of the pore water. In hydrology and geotechnical engineering, groundwater flow is described by gradients of hydraulic head, whether in saturated or partially saturated zones.

Pore water also governs solute transport within soils and rocks, carrying dissolved substances and affecting nutrient cycles, contaminant migration, and geochemical reactions. Its chemistry—pH, salinity, ionic strength—can influence mineral dissolution and precipitation, corrosion, and biological activity. Pore-water samples are routinely collected for environmental monitoring and geochemical analyses.

Measurement tools include piezometers for pressure head in saturated zones and tensiometers for matric suction in unsaturated soils. Field and laboratory methods vary with saturation state and objectives, but the concept of pore water remains central to understanding fluid flow, stability, and transport in porous media.